DESCRIPTION (APPLICANT'S ABSTRACT): We are using C. elegans vulval differentiation as a model system to study the mechanisms of cell differentiation and morphogenesis. Vulval differentiation in C. elegans is controlled by multiple cell signaling and regulatory pathways that are evolutionarily conserved with those commonly involved in controlling development in mammals and in human diseases such as cancers. For the next granting period, we will focus our studies on interactions among several regulatory (1) Analyzing the roles of two genes defined by suppressors of a ras mutation. (2) Identifying and characterizing targets and co-factors of two transcription factors acting downstream of RAS/MAPK using large scale genetic screens as well as a molecular screening method. (3) Analyzing the regulation of Iin-39 hox by several other factors and analyzing its connections to other regulatory pathways. (4) Dissecting two genes regarding their roles in a specific vulval morphogenesis event. Significant progress has already been made on proposed research.